A 42-year-old man comes to the office due to numbness and tingling in both legs and difficulty walking for the past several months. He has also noticed that he tires more easily with physical activity. His temperature is 36.8 C (98 F), blood pressure is 122/86 mm Hg, pulse is 76 /min, and respirations are 14/min. Physical examination shows conjunctival pallor and loss of vibration and position sensation in the bilateral lower extremities with associated gait ataxia. The remainder of the examination is within normal limits. Which of the following findings is most likely to be present upon further questioning of the patient?

Question

A 42-year-old man comes to the office due to numbness and tingling in both legs and difficulty walking for the past several months.  He has also noticed that he tires more easily with physical activity.  His temperature is 36.8 C (98 F), blood pressure is 122/86 mm Hg, pulse is 76 /min, and respirations are 14/min.  Physical examination shows conjunctival pallor and loss of vibration and position sensation in the bilateral lower extremities with associated gait ataxia.  The remainder of the examination is within normal limits.  Which of the following findings is most likely to be present upon further questioning of the patient?

Quizplus · Accepted Answer

11ec160b_36d8_50f1_9249_496aa36878ab_MD0001_00 Vitamin B12 (cobalamin) is obtained solely from the diet, specifically from animal products such as meat, dairy, and fish. Vitamin B₁₂ cannot be obtained from plant products, placing strict vegans at risk for dietary deficiency. The body is capable of storing about 1,000 times the daily requirement; therefore, vitamin B₁₂ deficiency develops only after the complete absence of intake for 4-5 years. The development of anemia as well as severe and potentially irreversible neurologic damage can result from vitamin B₁₂ deficiency. Red blood cell synthesis relies on vitamin B₁₂-dependent recycling of folate; deficiency of either vitamin results in a megaloblastic anemia. Neurologic symptoms vary in severity, but patients typically present with both motor and sensory deficits. Impaired myelin synthesis, specifically in the dorsal and lateral columns, results in subacute combined degeneration of the spinal cord. This condition is progressive and begins as a symmetrical neuropathy consisting of paresthesias and weakness. Ongoing deficiency leads to loss of vibration and position sensation with development of an ataxic gait. The longer the deficiency is untreated, the less likely it can be reversed. (Choice A) Isoniazid, one of several drugs used to treat tuberculosis, may result in vitamin B₆ deficiency. Clinical manifestations consist of stomatitis, cheilosis, atrophic glossitis, sideroblastic anemia, and peripheral neuropathy. However, this patient's lack of oropharyngeal findings makes vitamin B₆ deficiency less likely. (Choice C) Patients undergoing total gastrectomy will inevitably develop B₁₂ deficiency if not given vitamin supplementation. However, this deficiency takes years to develop due to the large hepatic B₁₂ reserve, and would not occur after a period of only 8 months. (Choice D) Phenytoin, an anti-epileptic drug used to treat both focal and generalized seizures, may result in folate deficiency and development of megaloblastic anemia. Phenytoin can also cause peripheral neuropathy, but this side effect usually only occurs with chronic therapy (>1 year). (Choice E) Vitamin D deficiency can develop over the course of several months due to inadequate dietary intake and minimal sunlight exposure. This deficiency presents as rickets in children and osteomalacia or osteoporosis in adults. Educational objective: Vitamin B₁₂ is obtained through the diet solely from animal sources, which places strict vegans at risk for dietary deficiency. This deficiency takes years to develop due to the large hepatic B₁₂ reserve, and presents with megaloblastic anemia and potentially irreversible neurologic deficits (eg, paresthesias, weakness, ataxic gait).

A 42-Year-Old Man Comes to the Office Due to Numbness